The required delay to exactly synchronize the Turn-On at the valley,

TDELAY,canbecalculatedasbelow:

Equation 5

(5)

TDELAY=TVALLEY−TZCD−DELAY

In the equation

TZCD−DELAYrepresentsthedelaybetweenthedemagnetizationtimeandtheinstantoftimein

which the ZCD voltage crosses the triggering threshold

VZCDT:thisdelayisintherangeoffewtensnsupto

hundred ns but can be easily experimentally measured during converter’s operation.

The value of

VTBcanbedirectlyreadfromthecurvealso.

Once VTB voltage is known, the value of the resistor can be easily derived:

Equation 6

(6)

RDELAY= RTB

NAUXNSEC∙VOUTVTB−1

The resistor

RTBcanbecalculatedasreportedinDynamicblankingtime.

The

TDELAYissettothedefaultvaluewhenRDELAYislowerthan:

Equation 7

(7)

RDELAY_default< RTB

NAUXNSEC∙ VOUT

VD−ONMIN −1

Dynamic blanking time and valley synchronization functions can be disabled connecting TB to GND.

The decision if the function is used or not is taken at power-up: before the pin VDD reaches the VDD-ON threshold,

the current ITB-DIS (200 µA typ.) is sourced from the pin. If the TB pin voltage is below the VTB-DIS threshold (100

mV typ.), the pin is assumed to be connected to GND, the related circuitry is disabled, and the information is

latched until the next power-on.

Please note that to ensure a correct check of the disabling function, the resistor

RDELAYcannotbelowerthan:

Equation 8

(8)

RDELAYmin <VTB−DISmax

ITB−DISmin =750 Ω

5.9

TB pin configuration

The pin TB can be easily configured in different combinations, as reported in Table 6 and in Figure 21, Figure 22,

Figure 23, Figure 24.

Table 6. TB pin matrix configuration

Dynamic Blanking Time

Valley Synchronization

Schematic Configuration

Yes

Yes

Figure 21

No

Yes

Figure 22

Yes

No

Figure 23

No

No

Figure 24

VIPERGAN65

TB pin configuration

DS14005 - Rev 2

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